The present invention relates to circuit board protective technologies and, in particular, to a method and system for shielding a circuit board from electrostatic discharge without significantly inhibiting heat exchange between heat-producing components of the circuit board and an external environment.
It is common practice in the electronics industry to externally mount circuit boards on electromechanical components. As one example, FIG. 1 illustrates a circuit board that implements a disk drive controller externally mounted to a disk drive enclosure. The circuit board 101 has a relatively flat surface studded with various components 102-112, including integrated circuits, that rise above the surface of the circuit board 101. These raised components 102-112 are generally encased in ceramic shells that protect enclosed internal electronic circuitry from damage arising from electrostatic discharge as well as from abrasion and other mechanical damage. However, many of these components 102-112 produce significant amounts of heat, and are mounted on the exterior surface of the circuit board to allow the heat produced by the components 102-112 to easily exchange with an air stream forced over the surface of the circuit board 101 or with ambient air via convective cooling. The circuits printed onto the circuit board 101 as well as other smaller components affixed to the surface of the circuit board (not shown in FIG. 1) are not protected from electrostatic discharge or mechanical insult.
The circuit board is often directly mounted to an underlying electromechanical component. In FIG. 1, the circuit board 101 is mounted to a hard disk drive enclosure 113. External mounting of the circuit board has the advantage of exposing the heat-producing components 102-112 mounted to the circuit board 101 to an air stream or to ambient air external to the electromechanical component enclosure 113 to allow for cooling of the heat-producing components, but has the serious disadvantage of exposing the printed circuit board 101 to electrostatic discharge and mechanical damage installation of the electromechanical component from, a computer system or disk array.
Various methods have been used to alleviate the above-described disadvantage inherent in externally mounted circuit boards. One techniques involves enclosing the circuit board in a metal casing, although this technique has the disadvantage of considerably increasing the volume of the disk drive enclosure, since an air gap must be left between the metal casing and the circuit board through which air can be forced to cool the heat-producing components mounted to the circuit board. Thus, designers, manufacturers, and users of electromechanical devices having externally mounted circuit boards have recognized the need for a cost-effective and space-efficient method for protecting the externally mounted circuit boards from electrostatic discharge and mechanical damage.
The present invention provides a method and system for shielding a circuit board from electrostatic discharge and from mechanical damage. A circuit board shield that represents one embodiment of the present invention comprises a flat, plastic plate, including a thin, embedded conductive film or mesh with external dimensions roughly equivalent to those of the circuit board which the shield is designed to protect. The shield includes apertures at locations complementary to the locations of each heat-producing component affixed to the circuit board and having shapes and sizes complementary to the shapes and sizes of the corresponding circuit board components. The circuit board shield is thus designed to closely conform to the external surface of the circuit board, so that, when the circuit board shield is mounted on top of the circuit board, the various heat-producing components affixed to the circuit board fit into complementary apertures of the circuit board shield. The circuit board shield protects the surface of the circuit board from electrostatic discharge, via the embedded conductive film or mesh, and protects the surface of the circuit board from mechanical damage. The apertures within the shield allow heat-producing components affixed to the circuit board to remain exposed to the external environment, despite placement of the circuit board shield on top of the circuit board. The exposed components are protected from electrostatic discharge and from mechanical damage by their own protective enclosures.